Best summer spots by day / by night (Berlin)

Hi dear Berliners and expats living there,

I visited Berlin several times but I've never been there during the summer (call me crazy but I really like fall and snowy winters in Berlin actually) :-)

So this will be my first summer trip to Berlin and I'd appreciate if you could give me your favorite spots of the following summer activities:
- By day: having a drink outside and/or eating with some dj playing good electronic music (by the Spree or the Landwehrkanal)
- By night: having a drink in a bar (not a club) with a great atmosphere, friendly over 30 years old crowd, and either a terrace or a great view.

I know there are many places in the city, so why don't you give me your 3 favorite ones during the summer?

vielen Dank!
PS: I'll be there with a friend and we're definitely up for meeting other people for a drink, a picnic, a dinner...